I think you'd need to start with general, and split once you'd built it up, otherwise you'd end up with the same problem as the forum - a million sections with half a dozen posts spread between them. It would be good to maybe give people some guide questions to answer to give us a better idea of what they want to know though.
I like the idea of social currency. I think you could throw in free reviews or a free review once you got to x posts, that way you'd get the people that will pay for a review as they don't want to join a community and spend months earning the option, but you'll convert some of those to forum users when the want more info. And you'll get some that earning the free reviews by reviewing others and participating in the forum will be a selling point.
I'm not sure about experts, most forums have kudos/thanks type addons that you could use to get the community to vote for helpful reviewers and give them status. I know big name people would provide a pull, but does it just have to be them to be a good service? I like to think I'm occasionally useful, but no one outside of cre8ate would know who I was

Peer reviews are still helpful though, and the non expert opinion can be as useful sometimes. Plus, it can be easy to be in a bit of a bubble, a good portion of the people that post in the hospital couldn't name the top 5 SEO people anyway. Although some are well known in the industry, a lot of the small business owners wouldn't know them from joe blogs. We know the hospital can be really good so we just have to sell it.
I guess you could build on it and have the option to pay a specific reviewer (if they agree obviously) to take a look for you. It would be an incentive to offer reviews, to build up your reputation, so people picked you to pay for a review. That's maybe getting ahead of things though.
I don't think it would need to be a massive change to what we do now, but presented in a different way - like a website trying to sell a service rather than a squirrelled away bit of a forum.